We have noticed problems with edit history over the past few weeks, but have been unable to establish any kind of pattern. It doesn’t happen with all edits, only some. As far as I’m aware, the problems only occur with edits made by moderators, but I can’t say that for certain. There are various permutations.
The pencil icon appears beside the post to indicate it has been edited, but the history window is blank; neither version of the post appears.
Edits “disappear” altogether. The post remains as edited, but no record of the edit remains, and no pencil icon appears.
Related to the above, where both the OP and a moderator have edited the same post, the moderators edits disappear from the history, but the OP’s edits remain. The number next to the pencil icon only indicates edits made by the OP. Where the moderator has entered an edit reason, and the OP hasn’t, the moderator’s reason appears with the OP’s edit.